A prime requirement for valve seat inserts used in internal combustion engines is wear resistance. In an effort to achieve a combination of good heat and corrosion resistance and machinability coupled with wear resistance, exhaust valve seat inserts have been made as cobalt, nickel or martensitic iron based alloy castings. These alloys have been generally preferred over austenitic heat-resistant steels having high chromium and nickel content because of the presence of wear resistant carbides in the cast alloys.
Powder metallurgy has been adapted to valve seat insert manufacture because the net end shape is achieved more directly than can be done otherwise. It permits latitude to select unique compositions and also offers design flexibility for achieving geometries that permit better air flow compared to other conventional forming methods.